In the field of medical treatment such as ophthalmology, eye accommodation function state measurement has been demanded. For example, a device which objectively measures the eye accommodation function has been proposed, such as an eye accommodation function state measurement device disclosed in patent document 1.
In eye accommodation function state measurement, according to the patent document 1, the eye's refractive power is continuously measured in the same manner as in a known refractive power measurement method (e.g. method disclosed in patent document 2), and high-frequency components of the refractive power are calculated from the measured refractive power values to determine the eye accommodation function state. The method disclosed in the patent document 1 requires continuous refractive power measurement for high-frequency components of 1 Hz to 2.3 Hz. When the frequency is set at 1 Hz, an eye refractive power measurement section continuously measures the refractive power at intervals of 0.1 sec, for example. The continuous measurement is performed for about 20 sec/cycle at a number of positions while moving the target position (e.g. about eight cycles at eight positions).
In related-art eye accommodation function state measurement, when performing 20-sec measurements in eight cycles, the measurement is performed for 160 seconds in total. Since the subject must continuously stare at the target during the measurement, the subject becomes tense when the measurement continues for such a long time.
Moreover, the subject suffers from continuously seeing the target for 160 seconds.
As refractive power measurement data, three kinds of data (i.e. spherical power data, cylinder power data, and astigmatic axis data) need to be stored. Therefore, when measuring the refractive power for 160 seconds at intervals of 0.1 second, 4800 pieces of data in total must be stored. This poses a problem in which a storage section must have a high capacity.
Moreover, since the measurement results can be obtained after measuring the refractive power for 160 seconds, even if data necessary for calculating the eye accommodation function state is insufficient due to movement of the eye, occurrence of a number of blinks, or the like, the operator continues the measurement operation without knowing such a data insufficiency. Therefore, if a measurement error has occurred, the measurement must be carried out again from the start.    (Patent document 1) JP-A-2003-70740    (Patent document 2) JP-A-6-165757